The conditions for gaining a plenary indulgence
Pope Paul VI set down a number of norms relating to indulgences at the end of Indulgentiarum Doctrina. Norm 7 states:
To acquire a plenary indulgence it is necessary to perform the work to which the indulgence is attached and to fulfil three conditions: sacramental confession, Eucharistic Communion and prayer for the intentions of the Supreme Pontiff. It is further required that all attachment to sin, even to venial sin, be absent. If this disposition is in any way less than complete, or if the prescribed three conditions are not fulfilled, the indulgence will be only partial, except for the provisions contained in n.11 for those who are “impeded.”It is worth reading the other norms because they deal with some of the practical questions that arise from these conditions. It is “fitting” that Holy Communion and the prayers for the Holy Father are recited on the same day as the indulgenced work is performed. But the sacramental confession could be made “several days” before or after. This is often interpreted as “a week or so”. However, the Sacred Penitentiary, in the Decree The Gift of the Indulgence, stated:
It is appropriate, but not necessary, that the sacramental Confession and especially Holy Communion and the prayer for the Pope's intentions take place on the same day that the indulgenced work is performed; but it is sufficient that these sacred rites and prayers be carried out within several days (about 20) before or after the indulgenced act. (n.5)
The "Heroic Act of Charity"
Is it more charitable to gain indulgences for others than for oneself? There used to be a popular devotion called The Heroic Act of Charity whereby people offered to God for the souls in purgatory all the satisfactory works they would perform in their lifetime. This included all the indulgences gained by the person. However, it was a voluntary thing. More charitable? Perhaps a person who has sinned a lot needs to gain a plenary indulgence for themselves first! Maybe we don't need to worry. Offering indulgences for the souls in purgatory is certainly such a charitable thing to do that it would be a case where "charity covers many a sin."
Can you gain an indulgence for another living person?
No, only for yourself or for the souls in purgatory. We ask God for our indulgences to be applied to the souls in purgatory. The technical expression is per modum suffragii (by way of suffrage). The Holy Father has jurisdiction over the souls on earth but not over the souls in purgatory.
Do you have to be baptised, in a state of grace etc?
Yes. You need to be baptised and in communion with the Church because this is a matter of the Church's jurisdiction. You need to be in a state of grace because if the life of grace is killed by mortal sin, our good works cannot gain supernatural merit for ourselves. (However, Bellarmine was of the opinion that a person in mortal sin could gain an indulgence for the souls in purgatory because the soul in purgatory would not be posing any obstacle to grace. This view was disputed...)
Questions of intention
"In order that one who is capable may actually gain indulgences, one must have at least a general intention to gain them, but does this apply to when meeting the conditions for receiving the indulgence?" No. If you went to confession on Saturday, for example, you could decide on Tuesday to say the Rosary in a Church with the intention of gaining the indulgence. It would not matter that you had not intended to gain the indulgence at the time you went to confession.
A "general intention" can be made simply by praying at the beginning of the day, making the intention to obtain all the indulgences that you can gain that day. When you look at the works prescribed for partial indulgences, we could all gain lots of partial indulgences every day by making a general intention.
Detachment from venial sin
The most problematic condition is:
[…] the complete exclusion of any attachment to any sin, even venial,This is not a new provision in the reform of Paul VI. Lépicier in his book Indulgences, their origin, nature and development reported a controversy which was widely current in his own time. Some theologians considered that the actual gaining a plenary indulgence was very rare.
[…] whilst with regard to plenary Indulgences, they teach us in a dogmatical tone that exceedingly few are those who can gain it, and fewer still are those who actually do gain it – perhaps a holy nun in some remote corner of the world, or some saintly hermit dead to this life and its concupiscences. (page 341)In countering this severe view of indulgences, Lépicier observed that falling into venial sin is not the same as having an affection for venial sin:
From the first no man, however holy, excepting Christ, and His Blessed Mother, can call himself free; but many should be, and in reality are, free from the second. How can we imagine faithful souls, that are anxious to please God, and daily seal this desire with the Bread of Life – and their generation, thank God, is not extinct – how can we imagine such as these to be wilfully attached to that which, though not causing eternal death, yet is infinitely injurious to the Divine Majesty? (page 343)If there is any doubt about the more lenient view of “detachment from venial sin”, it is perhaps worth noting that this view was expressed in 1895 by a Roman professor of theology.
More recently, in the grant of an indulgence for the Year of the Eucharist, the Apostolic Penitentiary restated the conditions for gaining a plenary indulgence. However, when speaking of special conditions for those who are infirm, the official English translation reads:
[…] as long as they are totally free from any desire to relapse into sin, as has been stated above.We may treat the more “lenient” view as common teaching since the Church clearly intends to grant plenary indulgences that can be obtained by the faithful every day. It would not seem reasonable to do this if it were almost impossible to gain them in practice.
We may therefore encourage people to carry out the works prescribed for the gaining of a plenary indulgence (including, for many, a return to the sacrament of confession) without discouraging them by the rigorist opinion that a plenary indulgence can scarcely ever be gained in fact. It is also a good thing to pray before doing the indulgenced work, asking God to take away all affection for venial sin and conceiving in our hearts a hatred of any sin since all sins displease God who loves us so much.